Synergistic enhancement of methane production from anaerobic digestion of spent mushroom substrate via addition of biochar and cerium chloride following compost pretreatment

The difficult degradation of fermentation substrate is the problem that restricts the anaerobic digestion (AD) of spent mushroom substrate (SMS). To obtain a potential and efficient solution to improve poor stability and low reactor efficiency, this study investigated the synergistic effect of biochar + Ce3+ on AD of SMS under the condition of composting pretreatment (CP). The gas production results showed that CP shortened the lag phase of reaction, and then biochar + Ce3+ synergistically enhanced CH4 production. The cumulative CH4 yield of the biochar + Ce3+ group reached 69.69 L/kgVS, which was 22.3% and 16.2% higher than that of a non-CP with no additions group and a CP with no additions group, respectively. The high-throughput sequencing analysis revealed that CP increased bacterial richness and diversity, and the co-addition of biochar + Ce3+ was beneficial to the growth of Syntrophomonadaceae, Anaerolineaceae and Ruminococcaceae species. Hence, following composting pretreatment (CP), biochar and Ce3+ worked synergistically to increase CH4 production. This indicated that our proposed method improved the process efficiency of CH4 production from SMS fermentation.